What Is the Observed Relationship between Species Richness and Productivity?

Abstract

Understanding the relationship between species richness and productivity is fundamental to the management and preservation of biodiversity. Yet despite years of study and intense theoretical interest, this relationship remains controversial. Here, we present the results of a literature survey in which we examined the relationship between species richness and productivity in 171 published studies. We extracted the raw data from published tables and graphs and subjected these data to a standardized analysis, using ordinary least-squares (OLS) regression and generalized linear-model (GLIM) regression to test for significant positive, negative, or curvilinear relationships between productivity and species diversity. If the relationship was curvilinear, we tested whether the maximum (or minimum) of the curve occurred within the range of productivity values observed (i.e., was there evidence of a hump?).A meta-analysis conducted on the distribution of standardized quadratic regression coefficients showed that the average quadratic coefficient was negative (i.e., the average species richness-productivity relationship was curvilinear and decelerating), and that the distribution of standardized quadratic regression coefficients was significantly heterogeneous (i.e., the studies did not sample the same underlying species richness-productivity relationship).Looking more closely at the patterns of productivity-diversity relationships, we found that, for vascular plants at geographical scales smaller than continents, hump-shaped relationships occurred most frequently (41-45% of all studies). A positive relationship between productivity and species richness was the next most common pattern, and positive and hump-shaped relationships co-dominated at the continental scale. For animals, positive, negative, and hump-shaped patterns were common at most geographical scales, and no one pattern predominated. For both plants and animals, hump-shaped curves were relatively more common in studies that crossed community boundaries compared to studies conducted within a community type, and plant studies that crossed community types tended to span a greater range of productivity compared to studies within community types. Sample size and plot size did not affect the probability of finding a particular productivity-diversity relationship (e.g., positive, hump-shaped, etc.). However, hump-shaped curves were especially common (65%) in studies of plant diversity that used plant biomass as a measure of productivity, and in studies conducted in aquatic systems.

Species–energy relationships at the macroecological scale: a review of the mechanisms

“…Thus, when investigating plant species-energy relationships it may be circular to use plant biomass or its surrogates as a productive energy metric ; yet, over 50 % of investigations into such relationships use plant biomass to measure energy availability ( Fig. 1 in Mittelbach et al, 2001). To avoid this potential circularity, and to constrain the breadth of subsequent considerations, we confine our discussion to consumer speciesenergy relationships ; the mechanisms may, however, apply to primary producers.…”

“…Understanding the factors controlling this variation is regarded as one of ecology's most important challenges (Hutchinson, 1959;Brown, 1981;Rosenzweig, 1995;Gaston, 2000). Meeting this challenge is increasingly important, as understanding the mechanisms that control spatial variation in species richness may improve predictions of how biodiversity will respond to environmental change and help to deliver effective conservation (Kerr & Packer, 1999 ;Gaston, 2000 ;Mittelbach et al, 2001). That geographical variation in species richness correlates positively with energy availability was recognised in the 19th century (Wallace, 1878) and it has frequently been suggested that spatial variation in energy availability controls species richness (Hutchinson, 1959 ;Connell & Orias, 1964 ;Leigh, 1965 ;MacArthur & Pianka, 1966 ;Rohde, 1978;Schall & Pianka, 1978;Rickerson & Lum, 1980).…”

“…Species-energy relationships largely fall into one of two categories. Species richness may vary with energy along a monotonically increasing curve, or may initially increase but then decline at higher energy levels, forming a unimodal species-energy relationship ; spatial scale may influence the relative predominance of these patterns (Rosenzweig & Abramsky, 1993 ;Waide et al, 1999;Mittelbach et al, 2001 ;Whittaker, Willis & Field, 2003).…”

Interactions between pH and nutrients on benthic algae in streams and consequences for ecological status assessment and species richness patterns

“…good ecological status is supposed to reflect a resilient ecosystem with a high level of adaptive capacity (Josefsson & Baaner, 2011). Ecosystem productivity and resource use efficiency are important ecosystem functions, and the general view today is that both generally depend on primary producer taxon richness, though variations in the shape of the productivity-diversity relationship are observed among individual studies (Mittelbach et al, 2001;Ptacnik et al, 2008). Our data suggest that the relative influence of diatoms and non-diatom benthic algae on ecosystem structure and functioning will vary in response to both pH and nutrient supply.…”

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

“…Mittelbach et al (2001) provided the first large-scale, formal meta-analysis of diversity−productivity relationships, based on 257 datasets, both terrestrial and aquatic, from 171 publications. Their central findings were that there is no single general pattern and that patterns are scale and taxon dependent, with local diversity most often demonstrating a unimodal (hump-shaped) response.…”